This project studies the developmntal control of expression of the two types of 5s RNA genes (5s DNA) in the frog Xenopus. Somatic cells produce a single kind of 5s RNA, while oocytes synthesize an additional 5s species. A developmental control mechanism appears to shut off oocyte 5s DNA in somatic cells. We will complete the sequencing of the variant genes in a clone of X. borealis oocyte 5s DNA (Xbo3) and test each gene's transcription capacity in an in vitro system. This will allow us to determine in what genetic region sequences produce an effect on transcription control. The pattern of 5s DNA transcription in vitro, when the DNA is added in the chromatin form, will also be studied. We also will look for differences in the chromatin stucture associated with oocyte versus somatic 5s genes.